This statements in this section merely provide background information related to the present disclosure and may not constitute prior art. A seat belt system for a vehicle typically includes a seat belt retractor with a seat belt webbing. Generally, the seat belt webbing is winding-up or coming out from the seat belt retractor. The seat belt maintains a relatively low level force on a vehicle occupant tending to pull him back into the vehicle seat in a comfortable manner, but allowing him to move forward to adjust a Global Positioning System (GPS) or a car radio and so forth. Accordingly, during normal driving conditions, the seat belt retractor does not restrict the freedom of movement by wearing the seat belt. An acceleration sensor detects acceleration or deceleration above a predetermined level as an indication of an emergency such as a collision, and locks the seat belt retractor against the further payout of the seat belt webbing to securely restrain the vehicle occupant in the vehicle seat.
Modern seat belt systems include an energy absorption feature to absorb or reduce the kinetic energy of the seat belt system. Accordingly, the seat belt system with the energy absorption feature allows some controlled payout of the seat belt webbing before it is fully locked, so as to more gradually decrease the momentum of the vehicle occupant. By reducing the kinetic energy of the seat belt with the energy absorption feature of the seat belt retractor, such as by slowing a pay-out rate or the seat belt and/or reducing a force applied to the seat belt may provide improved performance.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.